1. Field of the Invention
The present invention relates generally to a tensioner for applying an appropriate tension to a timing chain or timing belt of an engine, and more particularly to a tensioner equipped with a plunger stopper pin that holds a spring-loaded plunger in position against movement in a direction projecting from the tensioner body before the tensioner is assembled to the engine.
2. Description of the Related Art
A tensioner is used with a timing chain arranged to transmit a power between a crankshaft and a camshaft of an engine. The tensioner has a plunger that is urged by a spring to thrust outward from the tensioner body. When the tensioner is to be assembled to the engine, the plunger is needed to be pushed inside the tensioner body in advance against the force of the spring.
Accordingly, in the tensioner disclosed in the Japanese Patent No. 2895784, a stopper pin is inserted through a pin hole in the tensioner body into a pin hole in the plunger to thereby lock the plunger in position against the movement in a direction projecting from the tensioner body.
Another tensioner disclosed in the Japanese Patent Laid-open Publication No. HEI-7-42804 includes a plunger having a annular pin stopper groove formed therein, and a stopper pin inserted through a hole in the tensioner body into the pin stopper groove until a front end of the pin is caught by a side wall of the pin stopper groove. Thus, the plunger is prevented from thrusting out.
However, since the stopper pins used in the conventional tensioners comprise a needle-like stopper pin, the pin hole or the pin stopper groove formed in the plunger must be aligned with the pin hole in the tensioner body before the needle-like stopper pin is inserted. When the stopper pin is inserted through from the outside of the plunger or the outside of the tensioner body, the pin hole on the tensioner body or the pin stopper groove on the plunger lies in hiding. This makes it impossible to visually confirm the position of the pin hole or the pin stopper groove. Accordingly, it is very difficult to carry out the work to insert the stopper pin therein, and a great deal of time has been required for the work to insert the stopper pin.
Further, in the conventional tensioner having an annular pin stopper groove formed in the plunger, the man-hour to form the stopper groove is additionally needed.
It is therefore an object of the invention to provide a tensioner having structural features which can hold a plunger onto a tensioner body with a simple structure.
Another object of the invention is to provide a tensioner having a stopper that can be easily mounted to the tensioner body by a visual confirmation.
A further object of the invention is to provide a tensioner capable of easily holding a plunger to the tensioner body by a stopper pin, utilizing the shape and structure of an existing component.
According to the present invention, there is provided a tensioner comprising: a tensioner body; a plunger slidably mounted on the tensioner body and normally urged in a direction to project outward from the tensioner body; and a substantially U-shaped stopper pin having opposite end parts hooked on a part of the tensioner body and a part of the plunger, respectively, to hold the plunger in position against movement in the direction to project from the tensioner body.
In one preferred form of the invention, the tensioner body has a pin retaining hole formed in an outer surface thereof and extending perpendicularly to the axis of the plunger, and the plunger has a plastic shoe provided as an integral part on a front end of the plunger, the shoe having a pin retaining hole formed therein and extending perpendicularly to the axis of the plunger. One of the opposite end parts of the U-shaped stopper pin is engaged in the pin retaining hole in the tensioner body, and the other end part of the U-shaped stopper pin is engaged in the pin retaining hole in the shoe.
It is preferable that the stopper pin is formed from a resilient metal wire. The pin retaining hole in the tensioner body has a diameter slightly larger than the diameter of the metal wire of the stopper pin, and the retaining hole in the shoe is a rectangular hole much larger in diameter than the metal wire of the stopper pin.
When the plunger is to be locked in its retracted position, the plunger is pushed into the tensioner body, then the stopper pin is attached to the tensioner body and the shoe such that the opposite end parts of the stopper pin are engaged in the respective pin retaining holes of the tensioner body and the shoe. Since the pin retaining holes are formed on the outside surfaces of the tensioner body and the shoe, the pin attachment work can be easily achieved under visual observation. The pin retaining hole in the shoe is much larger in diameter than the stopper pin. This facilitates smooth attachment of the stopper pin to the shoe.
When the U-shaped stopper pin is in its free state, the opposite end parts of the stopper pin may be inclined toward each other. The inclined opposite end parts can exert an increased retaining force on the plunger.
The U-shaped stopper pin further has a center part extending between the opposite end parts. The center part is spaced from the tensioner body and the shoe in a radial direction of the plunger. The center part thus arranged can be easily gripped when the stopper pin is to be removed from the tensioner.
In another preferred form of the invention, the tensioner body has a pin retaining hole formed in an outer surface thereof and extending perpendicularly to the axis of the plunger, and the plunger has a pin retaining hole formed in an outer surface thereof and extending perpendicularly to the axis of the plunger. One of the opposite end parts of the U-shaped stopper pin is engaged in the pin retaining hole in the tensioner body, and the other end part of the U-shaped stopper pin is engaged in the pin retaining hole in the plunger. The pin retaining hole in the tensioner body and the pin retaining hole in the plunger may have a diameter slightly larger than the diameter of the metal wire of the stopper pin, and the opposite end parts of the stopper pin may be parallel to each other.
In a further preferred form of the invention, the tensioner body has a pin retaining hole formed in an outer surface thereof and extending perpendicularly to the axis of the plunger, and the plunger has a front end face extending perpendicularly to the axis of the plunger. One of the opposite end parts of the U-shaped stopper pin is engaged in the pin retaining hole in the tensioner body, and the other end part of the U-shaped stopper pin is engaged on the front end face of the plunger.
The stopper pin may have a center part extending between the opposite end parts and looped to form a rink-like pull tab. The ring-like pull tab facilitate the stopper pin removing work.
The above and other objects, features and advantages of the present invention will become apparent to those versed in the art upon making reference to the following detailed description and accompanying sheets of drawings in which a preferred structural embodiment of the present invention is shown by way of illustrative example.